Without limiting the scope of the invention, its background is described in connection with the controlled release of active agents, e.g., pharmaceutical agents.
One such patent is U.S. Pat. No. 6,335,033, issued to Oshlack, et al. for melt-extrusion of multiparticulates in which a unit dose sustained-release oral dosage form is taught containing a plurality of melt-extruded particles, each consisting essentially of a therapeutically active agent, one or more retardants, and optional water-insoluble binders. The particles have a length of from about 0.1 to about 12 mm and can be of varying diameters and each unit dose provides a release of therapeutically active agents over at least about 8 hours. Methods of preparing the unit doses as well as extrusion processes and methods of treatment are also disclosed. However, the release profile is determined by the type of melt-extrusion. Furthermore, the melt-extrusion process fails to address the need for the release of drugs that are in fragile multiparticulates. The drug release in this patent is governed by the properties of the thermoplastic carrier polymer and not by the particles.
Yet another patent is U.S. Pat. No. 6,743,442, issued to Oshlack, et al. for melt-extruded orally administrable opioid formulations. Briefly, a bioavailable sustained release oral opioid analgesic dosage form is described comprising a plurality of multiparticulates produced via melt extrusion techniques. This patent claims a sustained-release pharmaceutical formulation comprising an extruded blend of a therapeutically active agent, one or more hydrophobic materials selected from the group consisting of alkylcelluloses, acrylic polymers, and mixtures thereof; and one or more hydrophobic fusible carriers having a melting point from about 30° to about 200° C. and selected from the group consisting of natural or synthetic waxes, fatty acids, fatty alcohols, and mixtures thereof, the extruded blend divided into a unit dose containing an effective amount of the therapeutically active agent to render a desired therapeutic effect and providing a sustained-release of the therapeutically active agent for a time period of from about 8 to about 24 hours, the extruded blend being formed by mixing the therapeutically active agent, the one or more hydrophobic materials, and the one or more hydrophobic fusible carriers in an extruder to form the blend and extruding the blend through the extruder. Again, the release profile is determined by the type of melt-extrusion and it fails to address the need for the release of drugs that are in fragile multiparticulates. Again, the drug release in this patent is governed by the properties of the thermoplastic carrier polymer and not by the particles.
One approach as disclosed in patent application WO 2008/101743 (Gryczke 2008) involves the blending of an anionic polymer exhibiting a low glass transition temperature but too high permeability (Eudragit FS) with a water-insoluble polymer (Eudragit RS, RL or NE) to reduce the release in acid.